The aim of our work was to investigate the daytime-dependent effects of the fungal elicitor chitosan (CHT) on the local and systemic defence responses of intact tomato plants. Besides examining the circadian regulation of various physiological and molecular changes, we aimed to better understand their direct, light-derived as well as ethylene (ET)-dependent regulation, by studying ET insensitive Never ripe (Nr) mutant tomato plants. Further, in the second half of our work, we detected the local and systemic effects of the bacterial microbe-associated molecular pattern (MAMP) flagellin22 (flg22) at two different time points of the day based on our preliminary observations, especially their ET dependence. In addition to investigate the rapid, time-of-day- and light-dependent flg22-induced defence progression, their effects on providing long-term resistance were also analysed.